Can you determine which instances reflect a valid experiment or conclusion? Check only those that are valid.

A biology class is conducting an experiment to determine how soil pH affects the germination of pine seedlings. 30 pine seeds are placed in pots of soil with varying pH levels: 4.5, 6.5, 7.0, 7.5, 8.5, and 9.0. Pot size, water, and light exposure were constant for all pots.

A marine biologist is examining the effects of oil pollution on a population of seagulls (Larus canus). He is particularly interested in determining whether oil pollution reduces the number of eggs that may be hatched in each seagull nest. During one breeding season, he has counted the number of eggs present in 16 seagull nests and recorded the distance from each nest to a nearby oil refinery.

After months of grueling research drinking many, many colas, Karl has come to the conclusion that Brand A cola tastes better than Brand B cola.

Jeanette was conducting an experiment to determine if plants grow better when exposed to rap music. She bought two identical plants and exposed one to rap music for two weeks while the other grew without music. From the data, Jeanette determined that plants do not grow better with rap music.

Robert is instructed in a lab experiment to first record the ambient temperature of the room. To do this, he holds the thermometer under a bright light to accurately read it. He then reads and records the data as 33°C.